Painting the inside of a water tank?

I've no direct experience of them, having a SS tank, but coating materials for use on GRP tanks for drinking water approved under WRAS, the Water Regulations Advisory Scheme (WRAS Home), are available - some in small quantities at relatively modest cost. I would look amongst those and check suitability for small tanks and coverage with suppliers. I've seen this one at about £37 for a litre, which I imagine would be plenty: Potable Water Coating | Water Tank Reline MAXLINE 100 | MaxKote | UK and perhaps even smaller quantities of some may be available. (No connection etc.)
 
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john_morris_uk said:
What are the dimensions of the triangular one please? The space is more of a slice of a sideways pyramid...
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That's similar to what mine looked like. I had some osmosis 'pimples' forming in the tank (which constructed as part of the inner hull lining). I sanded-back surface and burst/drained the bubbles, then let it dry for a few weeks. Cleaned it all up with acetone then sealed the whole lot with the 3M stuff. It sets rock-solid and I'm hoping it will hold any further degradation of the structure at bay. Certainly nothing visible a couple of months ago. I also wondered about fitting a bladder but came to the conclusion that getting a custom-fit was too expensive and that the plastimo triangular tank wouldn't have fitted well in the space I had (almost a trapezoidal/pyramid shape). Then, I'd have needed to play-around with all the plumbing. Overall, sticking on a coat of 'paint' and replacing the tank lid was actually quite easy. Given you've got the lid off, you're only a few man-hours away from having the tank coated.
 
My water tanks are stainless steel and I would go for a stainless steel liner for that tank as it looks easy to slide on from the top.

You could also get a plastic water tank fabricated from one one like tek tanks that would fit in the existing tank space.
 
john_morris_uk said:
What are the dimensions of the triangular one please? The space is more of a slice of a sideways pyramid...
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Free Range Sailing on Youtube have just completed a major refit, including rebuilding their forward water tank. They didn't have any qualms about using food safe epoxy, and Troy (the bloke) seems to be pretty fastidious about things like that. Perhaps whilst you've got it open you'd like to think about internal baffles to stop any sloshing sound. I know there are some who are weary of built-in tanks (Bruce Robert being one) but the built-in tank in Mirrool had definitely saved it from sinking at some time in the past.
 
I had a smelly old flexible tank on board when I got the boat. I removed it and always used bottled water. Often the 5ltr square ones from lidl or aldi. But my wife finds them too big to handle easily. 6 packs of 2ltr bottles are cheap also and can be easily refilled hygienically as long as no one swigs from them directly.

Remove and/or replace the tank, or use food grade gerry cans or disposable bottles (I try ensure we recycle them after use).

Tank water is a risk even with modern well maintained systems. Drinking bad water would ruin your weekend cruise.
 
I would just scrub, flush and use the tank as designed. Bladders are horrible, you can't clean them out, but the original tank is easy to open and clean, with that lovely big inspection hatch.
May I ask, why is the 'permeability' a concern? I would never paint a drinking water tank on the inside, what for?
(apart from a cement wash inside large, mild steel fresh water tanks to slow down the rust)
 
Caraway said:
Seems a bladder is the better route. West System for water tanks
A couple of links mention bladder cancer and epoxy. Changing the resin/hardner ratios is suggested to overcome leaching problems with uncured components.

Even food safe epoxy is only approved for brief contact What is Food Safe Epoxy and Where to Buy It?
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Better tell Beneteau about that then, both mine had/ have tanks formed in the inner skin. They get osmosis blisters in. As for bladder tanks, yuk is what Ive heard about them getting slimy inside.
 
This thread has jogged a memory...I once took a stanley knife to an old freshwater bladder tank which had been retro-fitted to my 1970's Hurley.
Similar situation to the OP's.
The inside was smelly and crawling, I nearly retched, you just can't clean them.
 
Rogershaw said:
My water tanks are stainless steel and I would go for a stainless steel liner for that tank as it looks easy to slide on from the top.

You could also get a plastic water tank fabricated from one one like tek tanks that would fit in the existing tank space.
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Proper job.

Personally, I don't want to be drinking any water where amateurs have been mucking about with carcinogeninc chemicals in backyard conditions.
Maybe I'm unreasonably fussy in that way.
 
The two things needed are:
Large inspection hatch for scrubbing.
Not painted inside.

The OP's yacht has these already.
 
TernVI said:
Proper job.

Personally, I don't want to be drinking any water where amateurs have been mucking about with carcinogeninc chemicals in backyard conditions.
Maybe I'm unreasonably fussy in that way.
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I don't want to drink water contaminated with carcinogenic chemicals either - which is why I asked the question originally.

It looks as though a proper job will be coating with Potable Water Coating | Water Tank Reline MAXLINE 100 | MaxKote | UK and me ensuring that the manufacturers application sheet is followed meticulously.
Not a problem for me to monitor temperature and humidity when the boat is sitting next to a 230 volt supply on our drive way.
In my experience a good amateur often outperforms the professional in these areas. The professional just wants to get on with the next job and isn't always as fastidious as time is money. The disadvantage that the amateur has is that it takes them ages longer as they lack experience but time is not a problem for me atm.
 
Gary Fox said:
The two things needed are:
Large inspection hatch for scrubbing.
Not painted inside.

The OP's yacht has these already.
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Except the inspection hatch was riveted on with about thirty rivets so not easy to inspect. The reason I drilled the rivets out was that daughter was worried the whole thing would be full of slime. In fact it wasn't, but while it's off, I might as well give it a coat of potable tank lining paint. The boat was very much built down to a budget originally and I'm not sure the paint even existed back then.
 
Rogershaw said:
My water tanks are stainless steel and I would go for a stainless steel liner for that tank as it looks easy to slide on from the top.

You could also get a plastic water tank fabricated from one one like tek tanks that would fit in the existing tank space.
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We could do, and the water tanks in Serenditpity are all stainless. But for Eowyn the Pandora, a stainless one would add a lot of weight in the wrong area of the boat and it would be a bit OTT perhaps. It's only a 7 metre boat and I suspect that it's already being gilded beyond any other Pandora 700! Also I've thrown enough money at the boat already and a new suit of sails would be a priority ahead of a bespoke water tank potentially costing a few hundred £
 
Gary Fox said:
I would just scrub, flush and use the tank as designed. Bladders are horrible, you can't clean them out, but the original tank is easy to open and clean, with that lovely big inspection hatch.
May I ask, why is the 'permeability' a concern? I would never paint a drinking water tank on the inside, what for?
(apart from a cement wash inside large, mild steel fresh water tanks to slow down the rust)
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That is just not the case with the Plastimo type I linked to which have removeable (and replaceable) bladders. Just dose them with your favourite water treatment just as you would a solid tank. used one for 20 years before bladder needed replacement without any problems.

A cheap and effective solution to water supply on a small boat with small and irregular spaces for water storage.
 
john_morris_uk said:
Except the inspection hatch was riveted on with about thirty rivets so not easy to inspect. The reason I drilled the rivets out was that daughter was worried the whole thing would be full of slime. In fact it wasn't, but while it's off, I might as well give it a coat of potable tank lining paint. The boat was very much built down to a budget originally and I'm not sure the paint even existed back then.
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Thirty rivets, blimey. Will you replace them with self-tapping screws or something?
 
Here's a thought and a short explanation.

For ages we had a leaky built in fw tank on our liveaboard yacht. Tried all sorts then in the end, took the tank top off and painted several coats with a two part epoxy. I can't remember what it was, but we didn't die. Lots of curing time followed by four top up and empties to be safe. Still didn't ever use it to drink directly from tap tho. Was probably six or seven years ago.

So co incidentally to this thread, was down boat yesterday, leak has returned. It's clearly a design snag.

Ok, so we moved ashore and in common with lots of Canarian properties, we got a fresh water cistern under the patio. It's called an aljibe. It was never lined by the original builders and always concerned me that it might leak. Turns out there is a local firm that specialises in putting a potable water liner inside as this is a common fault. Related to the builder? ? So we got that done. I don't know what the material is though but now the leak has reappeared on the boat, I'm gonna find out and get it done inside the tank.

Nothing here happens quickly but when I find out what the material is, I can make a post.

So all that waffle says, actually, try a proper plastic sheet liner!
 
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